The present application relates generally to nuclear fuel rods; and more particularly to, a system for assembling or disassembling a segmented rod of a nuclear fuel bundle used within a nuclear reactor pressure vessel.
FIG. 1 is a schematic illustrating an environment in which an embodiment of the present invention may operate. FIG. 1 illustrates a typical nuclear processing facility 10, which may comprise a spent fuel pool 12, and a reactor pressure vessel (RPV) 15.
FIG. 2 is a schematic illustrating the RPV 15 of FIG. 1. During operation of the reactor, cooling water circulating inside a RPV 15 is heated by nuclear fission produced in the nuclear fuel core 35. Feedwater is admitted into the RPV 15 via a feedwater inlet 17 and a feedwater sparger 20. The feedwater flows downwardly through a downcomer annulus 25, which is an annular region between RPV 15 and a core shroud 30.
The core shroud 30 is a stainless steel cylinder that surrounds the nuclear fuel core 35, which includes nuclear fuel bundle assemblies 40, only a few are illustrated in FIG. 2, having a plurality of segmented fuel rods 43. A top guide 45 and a core plate 50 support each fuel bundle assembly 40.
The cooling water flows downward through the downcomer annulus 25 and into the core lower plenum 55. Then, the water in the core lower plenum 55 flows upward through the nuclear fuel core 35. In particular, water enters the fuel bundle assemblies 40, wherein a boiling boundary layer is established. A mixture of water and steam exits the nuclear fuel core 35 and enters the core upper plenum 60 under the shroud head 65. The steam-water mixture then flows through steam separators 70 on top of the shroud head 65 and enters the steam dryers 75, which separate water from steam. The separated water is recirculated back to the downcomer annulus 25 and the steam flows out of the RPV 15 and to a steam turbine, or the like, which is not illustrated in the Figures.
The BWR also includes a coolant recirculation system, which provides the forced convection flow through the nuclear fuel core 35 necessary to attain the required power density. A portion of the water is drawn from the lower end of the downcomer annulus 25 via recirculation water outlet 80 and forced by a recirculation pump (not illustrated) into a plurality of jet pump assemblies 85 via recirculation water inlets 90. The jet pump assemblies 85 are typically circumferentially distributed around the core shroud 30 and provide the required reactor core flow. A typical BWR may have between sixteen to twenty-four inlet mixers 95.
As illustrated in FIG. 2, a conventional jet pump assembly 85 comprises a pair of inlet mixers 95. Each inlet mixer 95 has an elbow welded thereto, which receives pressurized driving water from a recirculation pump via an inlet riser 97. A type of inlet mixer 95 comprises a set of five nozzles circumferentially distributed at equal angles about an axis of the inlet mixer 95. Here, each nozzle is tapered radially inwardly at the nozzle outlet. This convergent nozzle energizes the jet pump assembly 85. A secondary inlet opening may be located radially outside of the nozzle exits. Therefore, as jets of water exit the nozzles, water from the downcomer annulus 25 is drawn into the inlet mixer 95 via the secondary inlet opening, where mixing with water from the recirculation pump then occurs.
During the shutdown of the nuclear reactor, some of the segmented rods 43 may be removed from a fuel bundle assembly 40. These segmented rods 43 are then disassembled for further processing. The disassembly process is time consuming, delaying the processing and preparation of the segmented rods 43 before reentry into the RPV 15.
For the aforementioned reasons, there is a need for a system for disassembling a plurality of segmented rods 43 of a nuclear reactor core. The system should allow for simultaneously disassembling multiple segmented rods 43. The system should reduce the disassembly time and lower operator exposure to radioactivity.